• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.66.1-66.1
• /
• 2012

We have developed superconducting mixer receivers for 129 GHz VLBI observation in Korean VLBI Network(KVN). The developed mixer has a radial waveguide probe with simple transmission line LC transformer as a tuning circuit to its 5 series-connected junctions, which can have 125-165 GHz as operation RF frequency. For IF signal path a high impedance quarter-wavelength line connects the probe to one end of symmetric RF chokes. DSB receiver noise of the mixer was about 40 K over 4-6 GHz IF band whereas we achieved about uncorrected SSB noise temperature of 70 K and better than 10 dB IRR in 2SB configuration with 8-10 GHz IF band. Insert-type receiver cartridges using the mixers have been assembled for all three KVN stations. On-site performance summary in commissioning phase is presented.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.3 no.4
• /
• pp.88-94
• /
• 2004

High manganese steel was maintained stability of Non-Magnetics performance. Fatigue tests were carried out under constant stress amplitude, using a non-magnetic high manganese steel. The fatigue crack growth mechanism of the high manganese steel was clarified from results such as observation of crack growth path and fracture surface. The result of getting this study was shown as following: 1) Remarkably ${\Delta}Kth$ of the high manganese steel is big with about 3 times of the general steel product. 2) In the low ${\Delta}K$ value region, da/dN is dependent on Kmax, and in the high ${\Delta}K$ value region, it is dependent on ${\Delta}Keff$. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. 3) It seems to ease the stress concentration of crack tip crack growth behavior in the ${\Delta}Kth$ vicinity by the generation of the secondary crack.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.9
• /
• pp.631-638
• /
• 2020

The intention of this research is to identify the effect of corporate social responsibility (CSR) disclosure on firm value with profitability as a moderating variable. Data collection is carried out with data documentation that is based on financial reports and sustainability reports. All companies listed on the Indonesia Stock Exchange (IDX) during the 2013-2017 period are considered as the population of this study. Samples were selected using the purposive sampling method. The following are criteria that would be used in this study: 1) publish a sustainability report using the GRI G4 standard as a reference in preparing reports for 2013-2016, 2) publish a complete financial report for the 2014-2017 observation period, 3) not experience a loss during the 2014-2017 period. The total sample of the study was 109 companies. The study uses path analysis assisted with WarpPLS software version 6.0. The results show that the disclosure of corporate social responsibility has a positive and significant effect on firm value, and profitability moderates the effect of corporate social responsibility disclosure on firm value. The implication of the research is that implementing corporate social responsibility is very important to increase firm's value and firm's sustainability in the future.

• Korean Journal of Materials Research
• /
• v.11 no.4
• /
• pp.300-304
• /
• 2001

Effect of Cd addition on the fatigue properties of Al-Cu-Mn cast alloy was investigated by low and high cycle fatigue tests. With increasing Cd content, fatigue life and tensile strength were increased. It was found that the fatigue strength was 115MPa and the fatigue ratio was 0.31. Metallographic observation revealed that the fatigue crack initiated at the surface and propagated along the grain boundary. This propagation path was attributed to the presence of PFZ along the grain boundary. The tensile strength increased from 330MPa in the Cd-free Al-Cu- Mn cast alloy to 401MPa in the 0.15%Cd-containing alloy.

• Ocean and Polar Research
• /
• v.36 no.3
• /
• pp.225-234
• /
• 2014

The 2011 Tohoku earthquake triggered extremely destructive tsunami waves which propagated over the Pacific Ocean, Atlantic Ocean through Drake Passage and Indian Ocean respectively. A total of 10 tide-gauge records collected from the UNESCO/IOC site were analyzed through a band-pass digital filtering device to examine the observed tsunami characteristics. The ray tracing method and finite-difference model with GEBCO 30 arc second bathymetry were also applied to compare the travel times of the Tohoku-originated tsunami, particularly at Rodrigues in the Indian Ocean and King Edward Point in the Atlantic Ocean with observation-based estimates. At both locations the finite-difference model produced the shortest arrival times, while the ray method produced the longest arrival times. Values of the travel time difference however appear to be within tolerable ranges, considering the propagation distance of the tsunami waves. The observed tsunami at Rodrigues, Mauritius in the west of the Madagascar was found to take a clockwise travel path around Australia and New Zealand, while the observed tsunami at King Edward Point in the southern Atlantic Ocean was found to traverse the Pacific Ocean and then passed into the Atlantic Ocean through the Drake Strait. The formation of icebergs captured by satellite images in Sulzberger in the Antarctica also supports the long-range propagation of the Tohoku-originated tsunami.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.10 no.2
• /
• pp.101-106
• /
• 2010

We propose an approach to estimate the real-time moving trajectory of an object in this paper. The object's position is obtained from the image data of a CCD camera, while a state estimator predicts the linear and angular velocities of the moving object. To overcome the uncertainties and noises residing in the input data, a Extended Kalman Filter(EKF) and neural networks are utilized cooperatively. Since the EKF needs to approximate a nonlinear system into a linear model in order to estimate the states, there still exist errors as well as uncertainties. To resolve this problem, in this approach the Kohonen networks, which have a high adaptability to the memory of the inputoutput relationship, are utilized for the nonlinear region. In addition to this, the Kohonen network, as a sort of neural network, can effectively adapt to the dynamic variations and become robust against noises. This approach is derived from the observation that the Kohonen network is a type of self-organized map and is spatially oriented, which makes it suitable for determining the trajectories of moving objects. The superiority of the proposed algorithm compared with the EKF is demonstrated through real experiments.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.3
• /
• pp.103-115
• /
• 2003

This study examines groundwater movement system analysis and movement forecast algorithm using finite element method. The target is Cheongha-myeon area, Bukgu, Pohang-city which has many difficulties in water supply during drought period. From the comparison of the differences between obtained values by WINFlOW model and observed values, it is thought that groundwater head distribution under steady flow is reflected well at the level of reliability Groundwater movement of study area shows stable pattern from western watershed to eastern coastal area while flow path is dense and steep in the center of the coastal area. The results of particle tracing for each well show a comparatively straight line from the western boundary side to the observation position at the upper area of the well, and are analyzed as it diffuses according to getting closer to the coast at the lower area of the well. The result of effect circle examination attendant on pumping amount in study area shows variation tendency that groundwater head decreases at the side and the lower area more than at the upper area of the well when groundwater flows from west to east(coast). As mentioned above, satisfactory results of groundwater movement analysis using WINFlOW model, two dimensional groundwater movement analysis model, are obtained through the great decrease of physical uncertainty of groundwater movement system.

• Korean Journal of Materials Research
• /
• v.12 no.4
• /
• pp.248-253
• /
• 2002

Effect of Sn addition on the fatigue properties of Al-Cu-Mn cast alloy was investigated by low and high cycle fatigue tests. Fatigue life showed the maximum value of 5450cycles in the Al-Cu-Mn alloy containing 0.10%Sn, but decreased rapidly beyond 0.20% of Sn additions. It was found that the fatigue strength was 132MPa and fatigue ratio was 0.31 in the alloy containing 0.10%Sn. Metallographic observation revealed that the fatigue crack initiated at the surface and propagated along the grain boundary. This propagation path was attributed to the presence of PFZ along the grain boundary. The tensile strength increased from 330MPa in 7he Sn-free Al-Cu-Mn cast alloy to 429MPa in the alloy containing 0.10%Sn. But above 0.20%Sn additions, tensile strength was decreased by the segregation of Sn.

• Journal of the Korean Ceramic Society
• /
• v.33 no.1
• /
• pp.83-91
• /
• 1996

Monolithic AlN and AlN-W composites were fabricated by pressure-less sintering at 190$0^{\circ}C$ under nitrogen atmosphere and the influences of tungsten phase on the microstructure and mechanical properties were investi-gated. In the fabrication of sintered specimen no additive was used. And monolithic AlN showed substantial grain growth and low relative density. AlN-W composites were fully densified and grain growths of matrix were inhibited. The densification behavior of composites were inferred to be achieved through the liquid phase sintering process such as particle-rearrangement and solutino-reprecipitation. Also the oxid phases which is expected to form liquid phases duringsintering process were detected by XRD analysis. As the tungsten volume content increases fracture strength was decreased and fracture toughness was increased. It was suppo-sed that the strength decrease of composites with tungsten content was due to existence of interface phases. The subcritical crack growth behavior was observed from the stress-strain curve of composites. The effect of the secondary phase and interface phases on toughness in crease were studied through observation of crack propagation path and the influence of residual stress on crack propagation was investigated by X-ray residual stress measurement. In the result of residual stress measurement the compressive stress of matrix in composi-test was increased with tungsten volume content and the compressive stress distribution of matrix must have contributed to the inhibition of crack propagation.

• Korean Journal of Materials Research
• /
• v.30 no.3
• /
• pp.105-110
• /
• 2020

Cu/PET composite films are widely used in a variety of wearable electronics. Lifetime of the electronics is determined by adhesion between the Cu film and the PET substrate. The formation of an anisotropic nanostructure on the PET surface by surface modification can enhance Cu/PET interfacial adhesion. The shape and size of the anisotropic nanostructures of the PET surface can be controlled by varying the surface modification conditions. In this work, the effect of Cu/PET interface nanostructures on the failure mechanism of a Cu/PET flexible composite film is studied. From observation of the morphologies of the anisotropic nanostructures on plasma-treated PET surfaces, and cross-sections and surfaces of the fractured specimens, the Cu/PET interface area and nanostructure width are analyzed and the failure mechanism of the Cu/PET film is investigated. It is found that the failure mechanism of the Cu/PET flexible composite film depends on the shape and size of the plasmatreated PET surface nanostructures. Cu/PET interface nanostructures with maximal peel strength exhibit multiple craze-crack propagation behavior, while smaller or larger interface nanostructures exhibit single-path craze-crack propagation behavior.